In recent years, many image sensors with improved infrared sensitivity have been proposed. For example, for an image sensor using a silicon substrate, a proposed device includes a photoelectric conversion photodiode having a large thickness (e.g., 3 μm or more) to improve the infrared sensitivity because an infrared ray absorption coefficient of silicon is small. As a specific example, Japanese Unexamined Patent Publication No. 2003-60191 discloses an example of a photodiode having the thickness of 10 μm.